Yep, you are wise to employ the 301 permanent redirect to capture traffic from the old site. I have heard that you really don't have to keep those redirects in place for much longer than six months. Once people find your site through the redirects and adjust their bookmarks, you should feel comfortable removing those redirects after a time.
The benefits of using WP to drive your site are that it's search engine friendly right out of the box. Combine that with the myriad plugins that do nothing but enhance that and you are well on your way to a nicely optimized site without having to spend a fortune on an SEO expert. Of course, if that is a big concern of yours, you are prolly best to go ahead and do much more in the way of SEM, but as I said, it's a great START in the right direction with a minimum of effort on your part.
It is a very popular blogging app/CMS and I think it's at the apex of its popularity right now. This is good because it means that there are a lot of people who are very familiar with it so there's no shortage of help (this forum, independent tutorials, new ways to push the WP envelope) if you run into trouble. There are a vast array of plugins that let you do just about anything with WP.
The ability to edit your content online is great and it's as easy as typing in MS Word. (Although I discourage you from cutting and pasting from Word into WP. Word is *not* a text editor!) But the convenience of being able to add and edit content will keep you from dragging your feet about updating your site because it's a bigger PITA to write an HTML page and upload it to the site than it is to create or edit a post or page.